This project seeks to determine if reparative dentinogenesis can be induced by transient expression of the gene for OP-1 transduced into pulp cells in vivo. Our data demonstrate that recombinant osteogenic protein-1 (OP-1) will induce reparative dentin formation in animals when placed directly on partially amputated vital dental pulps. Since this local reparative process occurs sealed within the dental pulp, we propose that reparative dentinogenesis is a useful model to test the efficacy of gene therapy to treat acquired oral pathologic conditions. In this way controlled amounts of the recombinant adenovirus vector can be delivered to the tissue of interest and the local response compared directly with the known effects of exogenously added OP-1. Our general hypothesis is that OP-1, a signaling molecule, stimulates receptor-bearing resident dental pulp cells to initiate an uncharacterized cascade of events leading to reparative dentin. The protein is degraded, probably upon internalization by the cells, and thereby limited in action. Similarly limited production of OP-1 by transiently transduced cells could provide sufficient OP-1 to initiate reparative dentinogenesis. To our knowledge, no previous attempts to initiate tissue repair using recombinant adenovirus have been reported. Therefore we propose experiments to 1) develop an adenovirus vector containing a full length OP-1 cDNA insert, 2) examine its ability to induce OP-1 expression in vitro, 3) transduce pulp cells in vivo, 4) assess OP-1 expression in vivo, 5) assess expression of odontoblast markers and 6) assess reparative dentin formation. These experiments also seek to determine which genes are active within the responding cells and relate these events spatially and temporally to the formation of reparative dentin. Modern methods of histology, immunology, biochemistry and molecular biology applied both separately or in conjunction as appropriate will be utilized. A general hypothesis regarding tissue regeneration holds that the mechanisms of tissue formation involved mimic those of tissue formation during development. Therefore the initial focus will be on markers of odontoblast differentiation, such as type I collagen, dentin sialoprotein and dentin matrix protein-1, expressed during tooth development. The data generated will provide useful information regarding the general utility of gene therapy of oral tissues.